Measurement of Radiation Using Tissue Equivalent Phantom in ICR Treatment

자궁강내 근접방사선조사시 인체조직등가 팬톰을 이용한 방사선량 측정

  • Jang, Hong-Seok (Department of Therapeutic Radiology Catholic University Medical College) ;
  • Suh, Tae-Suk (Department of Therapeutic Radiology Catholic University Medical College) ;
  • Yoon, Sei-Chul (Department of Therapeutic Radiology Catholic University Medical College) ;
  • Ryu, Mi-Ryeong (Department of Therapeutic Radiology Catholic University Medical College) ;
  • Bahk, Yong-Whee (Department of Therapeutic Radiology Catholic University Medical College) ;
  • Shinn, Kyung-Sub (Department of Therapeutic Radiology Catholic University Medical College)
  • 장홍석 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실) ;
  • 서태석 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실) ;
  • 윤세철 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실) ;
  • 유미령 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실) ;
  • 박용휘 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실) ;
  • 신경섭 (가톨릭대학교 의과대학 강남성모병원 방사선과학교실)
  • Published : 1995.03.30

Abstract

This study is to compare A point doses in human pelvic phantom by film dosimetry, computer planning and manual calculation by using of along-away table. We developed tissue equivalent human pelvic phantom composed of four pieces of cylindrical acryl tubes with water, to simulate intracavitary radiation (ICR) in patients with cervix cancer. When the phantom assembled from 4 pieces, it has a small space for inserting Fletcher-Suit-Delclos applicator like a human vagina. Fletcher-Suit-Delclos applicator inserted into the space was packed tightly with furacin gauzes, and three $^{137}Cs$ sources with radioactivity of $15.7mg\;Ra-eq$ were inserted into the tandem. For the film dosimetry, two pieces of X-OMAT V film (Kodak Co.) of which planes include point A, were arranged orthogonally in the slits between phantoms. A point dose and iso-dose curves were measured by means of optical densitometer. A point doses by film dosimetry, RTP system and manual calculation by using of along-away table were compared, and iso-dose curves by film dosimetry and computer planning were also compared. The dose of A point was 51.2cGy/hr by film dosimetry, 46.7cGy/hr by RTP system and 47.9 cGy/hr by along-away table. A point dose by computer planning was similar to the dose by calculation using of along-away table with acceptable accuracy $({\pm}3%)$, however, the dose by film dosimetry was different from two others with about 10% error. Since most clinical beams contains a scatter component of low energy photons, the correlation between optical density and dose becomes tenuous. In addition, film suffers from several potential errors such as changes in processing conditions, interfilm emulsion differences, and artifacts caused by air pockets adjacent to the film. For these reasons, absolute dosimetry with film is impractical, however, it is very useful for checking qualitative patterns of a radiation distribution. In future, solid state dosimeter such as TLD must be used for the dosimetry of ionizing radiation. When considerable care is used, precision of approximately 3% may be obtained using TLD.